We propose continued participation in the Pediatric Oncology Group (POG). Our goals are as follows: (1) to improve cure rates for children with cancer through participation in Phase I, II, and III clinical trials designed to test new agents or concepts; and (2) to participate in laboratory-based research aimed at clarifying the basis of drug resistance and pathogenetic mechanisms of childhood cancers. We are committed to Group participation because we believe: (1) that collaborative efforts are both desirable and necessary for study of childhood cancers, since all are relatively rare; and, (2) that well-designed randomized clinical trials provide the most definitive test of efficacy and general applicability of new therapies and that pooled intellectual resources are advantageous as well. our contribution to the Group can be categorized as follows: (1) contribution of selected patients (those with rare tumors or less common stages of other cancers, n is approximately 60-70/year) to Group studies; (2) administrative and scientific leadership (Group vice-chairman; disease committee chairmen including pathology, psychology, brain tumor, and lymphoid; and protocol coordination); (3) provision of multiple reference laboratories [flow cytometry analyses of acute lymphoblastic leukemia (ALL), Ewing sarcoma, neuroblastoma, osteosarcoma and rhabdomyosarcoma, B and pre-B cell typing, cell bank for ALL and the solid tumors noted above]; (4) regular presentation of results of in-house research to the Group. Since our center has an unusually large number of patients and staff (both clinical and basic), the latter contribution assumes unusual importance. We have an extensive in-house developmental therapeutics program which is independent of, but complementary to, the Group's clinical research programs. We also have extensive programs in basic research. The aim of these programs, to determine the pathogenesis of pediatric neoplasia, is expected to positively influence the Group's central goal -- curing children with cancer.